How to use clairaut's theorem with 3rd order partial derivatives

In summary, Clairaut's theorem is a mathematical theorem used in calculus to simplify calculations involving partial derivatives. It states that the order of differentiation does not matter for mixed partial derivatives as long as the function has continuous second partial derivatives. This theorem can be applied to 3rd order partial derivatives and is used by taking the mixed partial derivative with respect to the two variables. However, there are limitations to using this theorem, as it only applies to functions with continuous second partial derivatives and not pure partial derivatives.
  • #1
physicsidiot1
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Homework Statement



Use Clairaut's Theorem to show that is the third order partial derivatives are continuous, then fxxy=fyxy=fyyz

Clairaut's Theorem being: fxy(a,b)=fyx(a.b)

Homework Equations



fxyy=d/dy(d2f/dydx)=d^3f/dy^2dx

The Attempt at a Solution



Tried to differentiate the second partial derivatives but it didn't work out.
 
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  • #2
counter example

Try when f = (x^3)(y^2)(z). After differentiating, try (5,7,11).
 

1. What is Clairaut's theorem and what is its use in calculus?

Clairaut's theorem is a mathematical theorem that states that if a function has continuous second partial derivatives, then the order of differentiation does not matter for the mixed partial derivatives. This means that the value of the mixed partial derivatives will be the same regardless of the order in which the variables are differentiated. It is commonly used in calculus to simplify calculations involving partial derivatives.

2. Can Clairaut's theorem be applied to 3rd order partial derivatives?

Yes, Clairaut's theorem can be applied to 3rd order partial derivatives. It states that the order of differentiation does not matter for any number of partial derivatives as long as the function has continuous second partial derivatives.

3. How do you use Clairaut's theorem to calculate 3rd order partial derivatives?

To use Clairaut's theorem to calculate 3rd order partial derivatives, you first need to make sure that the function has continuous second partial derivatives. Then, you can simply take the mixed partial derivative with respect to the two variables and the result will be the same regardless of the order in which the variables are differentiated.

4. What is an example of using Clairaut's theorem with 3rd order partial derivatives?

One example of using Clairaut's theorem with 3rd order partial derivatives is in calculating the third derivative of a function f(x,y,z) with respect to x and z. By applying Clairaut's theorem, we can take the mixed partial derivative with respect to x and z, and the result will be the same regardless of the order in which the variables are differentiated.

5. Are there any limitations to using Clairaut's theorem with 3rd order partial derivatives?

Yes, there are limitations to using Clairaut's theorem with 3rd order partial derivatives. It only applies to functions with continuous second partial derivatives, so it cannot be used if the function does not meet this criteria. Additionally, it only applies to mixed partial derivatives, not pure partial derivatives.

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